Lahore, Pakistan — The revelation that US immigrant and would-be bomber Najibullah Zazi received training in Pakistan is likely to prove somewhat damaging to the Pakistani government, already under fire for not following up on its military success in the Swat Valley and northern tribal regions with ground offensives in either North or South Waziristan.

In a case that US security experts have called one of the most significant threats to the country since Sept. 11, the young Afghan was indicted on Thursday by a federal grand jury in New York on suspicion of conspiracy to use weapons of mass destruction. According to an FBI dossier submitted before the court, Zazi "received detailed bomb-making instructions" in Pakistan, where he resided from August 2008 to January 2009 before leaving for Denver.

"Nobody is saying people haven't been coming here and have not been getting training," says a former Pakistani intelligence agency chief who spoke on condition of anonymity. While training camps in the northern tribal regions of Bajaur, Mohmand, and Khyber have now been dismantled and the situation has improved over the past year, he added, camps would continue to operate in the south until military operations there "are brought to their logical conclusion."

Meanwhile, militant training camps in the country are evolving into makeshift, fly-by-night arrangements that are more difficult for the authorities to close down, says Rifaat Hussain, a security expert at Quaid-e-Azam university in Islamabad.

"A training camp could be in the basement of a mosque. Every seminary has an associated training arrangement – they have makeshift equipment and before the security forces can move in they have shifted their arrangements," he says.

Details of where Mr. Zazi stayed, trained, or with whom he associated during his five-month stay in Pakistan remain sketchy. But Dr. Hussain ventures a guess.

"If he received training on the border area with Afghanistan, one can surmise that he has links with the Afghan insurgent groups and Al Qaeda," he says, adding one possibility might be a connection with the Haqqani network in North Waziristan that is used as a launch pad for operations into Afghanistan.

He adds that any information gleaned from Zazi could prove insightful to authorities. "Who were his handlers? How was he brought in? Who did he meet with? All these answers will prove very useful."